For a conventional rotating electric machine, for example, Japanese Patent Laying-open No. 2005-6428 discloses a rotor structure provided in a rotating electric machine for the purpose of cooling a motor's right and left stator coil ends uniformly (Patent Document 1). More specifically, Patent Document 1 discloses a rotor structure including: a rotation shaft coolant oil channel provided internal to a rotation shaft; first and second rotation shaft coolant oil branching channels receiving a coolant oil from the rotation shaft coolant oil channel and branching the oil in a direction perpendicular to the rotation shaft; first and second rotor coolant oil channels provided parallel to the rotation shaft and independent of each other; and first and second rotor end face oil channels provided at the rotor end faces in the form of a circumferential groove.
Furthermore, Japanese Patent Laying-open No. 9-182375 discloses a motor cooling circuit provided to cool a rotor's core to minimize eddy current loss, hysteresis loss and the like to minimize heat generation (Patent Document 2). More specifically, Patent Document 2 discloses a motor cooling circuit including: first and second axial oil channels passing through the core in an axial direction; an axial oil channel provided internal to a rotor shaft; first and second radial oil channels allowing the first and second axial oil channels and the axial oil channel internal to the rotor shaft to communicate with each other, respectively, to guide the oil that passes through the axial oil channel internal to the rotor shaft to the first and second axial oil channels; and a supply means. The supply means supplies oil which is in turn supplied centrifugally from the axial oil channel internal to the rotor shaft to the core and passes through the first and second axial oil channels and thus cools the core.
Furthermore, Japanese Patent Laying-open No. 2007-336646 discloses a rotating electric machine with an improved rotor cooling performance to eliminate the necessity of introducing a coolant chamber at a stator frame or the like and thus allow the rotating electric machine to be produced at a reduced cost in a reduced period of time, formed of a reduced number of components, applied in a wider range, and stabilized in quality (Patent Document 3). Furthermore, Japanese Patent Laying-open No. 2006-158105 discloses a motor cooling device allowing a coolant to be self-circulated in order to achieve a cooling system reduced in size and weight (Patent Document 4).
Furthermore, Japanese Patent Laying-open No. 2004-166492 discloses a vehicular electric motor cooling device preventing a coolant from contacting a magnet of a vehicle driving electric motor and thus degrading/altering the magnet (Patent Document 5). Furthermore, Japanese Patent Laying-open No. 2005-278319 discloses a motored power device configured to cool an electric motor's locally heated portion intensively while achieving reduced power loss (Patent Document 6).